About Microbicides
This section provides basic information on
microbicides, one of the options being tested
now as part of the effort to identify
additional tools to reduce the risk of HIV
transmission.
You can also download this information as a microbicide fact sheet (PDF).
What is a microbicide?
The term microbicide refers to various strategies being tested that may reduce the risk of HIV transmission during sex. These include creams, gels, and suppositories that could be used vaginally or rectally.
Why are we looking at microbicides?
The goal of a microbicide is to reduce the risk of HIV infection at the site of sexual exposure (vagina or rectum). There are several ways in which a microbicide might provide this protection. It might contain an active ingredient that blocks HIV activity directly, or it may act as a physical barrier at the mucosal lining of the vagina or rectum.
How will we know if microbicides work?
Every HIV biomedical prevention candidate goes through an extensive series of evaluations, first in laboratory and animal studies and then in humans. The animal studies provide preliminary information about the safety and effectiveness of the candidate. Only those candidates that appear safe in animals are considered for human testing. Efficacy data from animals can also be used to inform decisions about whether to test a candidate in humans. However, studies in animals cannot give a clear answer about whether a strategy will reduce HIV risk in humans. In microbicide animal studies, scientists control exactly when the drug is taken and when the animal is challenged with the infectious virus. Trials in humans provide information about how the strategy works in situations where product usage may not be 100 percent consistent and the timing of potential exposure to HIV is frequently not known.
Microbicide candidates that meet criteria in laboratory and animal studies are moved into small safety studies in humans (Phase I trials). Candidates that appear to be safe and meet certain criteria are then tested in expanded safety studies (Phase II trials). Some of the candidates that complete these stages are moved into large-scale efficacy or effectiveness trials, which may be called Phase III, Phase IIb, test-of-concept, or proof-of-concept trials. There are technical reasons why some trial designs are called efficacy and others are effectiveness studies. Both terms refer to trials that look at whether a candidate reduces the risk of HIV infection. For simplicity, the term efficacy is used below.
The details of these large-scale efficacy studies vary, but the design of microbicide efficacy trials is similar to that of most HIV prevention trials. These trials enroll healthy, HIV-negative people, most commonly in communities where researchers have conducted preparatory work to learn about the rates of risk behaviors and incidence. Each participant receives a basic prevention package including treatment for sexually transmitted infections, condoms, and behavior change counseling. [Unfortunately, needle exchange is not provided in all of the efficacy trials involving injection drug users, and this area is receiving continued attention from advocates and activists.] Some of the participants are randomly assigned to receive the experimental microbicide, while the other participants receive a placebo, a product that is indistinguishable from the experimental microbicide and has no effect on the body. No participant knows whether he or she is receiving the candidate microbicide or placebo. All participants are counseled at every study visit that they can't assume they will be protected by the microbicide and that they cannot know whether they have received the experimental microbicide or the placebo.
Over the course of the trial period, some participants get infected even though they are being counseled and receiving prevention services. This is consistent with what we know about the AIDS epidemic: even with information and services, not everyone can protect himself or herself all the time.
At the end of the trial, researchers compare the rates of new infections in the participants who received the experimental microbicide and in those who received the placebo. If there are significantly fewer new infections in the experimental microbicide group, that is, if the difference is greater than that which can be attributed by chance, this suggests that the microbicide is beneficial.
Where are microbicide trials taking place?
There are nearly 25 clinical trials of experimental microbicides currently underway, in 20 countries, with a concentration in East and Southern Africa. Most of these are small Phase I or Phase II studies. View our world map of ongoing microbicide and other biomedical HIV prevention research trials.
Who is participating in microbicide research?
Like other HIV prevention strategies, microbicide trials are conducted among different populations including gay men and other men who have sex with men, sex workers, and heterosexual men and women in sub-Saharan Africa. Both men and women participate in safety studies for rectal use of microbicides, and men participate in studies to assess penile safety.
When are results expected?
Results from the UK's Microbicide Development Programme's Phase III microbicide efficacy trial, known as MDP 301, are scheduled to be announced in November 2009. MDP 301 is testing the microbicide PRO 2000 to see if it works to reduce the risk of HIV transmission. For more on PRO 2000 and the efficacy trials in which it has been tested, please visit our page on anticipating and understanding the results from trials of the PRO 2000 microbicide candidate.
Results from CAPRISA 004, the first large-scale study of an antiretroviral-containing microbicide, are scheduled to be announced in 2010. In 2013, the VOICE study (MTN 003), another large-scale trial, is scheduled to release results. VOICE is evaluating three different strategies to prevent HIV in women: one ARV-containing microbicide and two different PrEP regimens that consist of taking oral ARVs on a daily basis.
Visit the HIV prevention research timeline and trials map for details on other ongoing biomedical HIV prevention research trials.
Click here for a table of ongoing microbicide trials.
You can also download this information as a microbicide fact sheet (PDF).
What is a microbicide?
The term microbicide refers to various strategies being tested that may reduce the risk of HIV transmission during sex. These include creams, gels, and suppositories that could be used vaginally or rectally.
Why are we looking at microbicides?
The goal of a microbicide is to reduce the risk of HIV infection at the site of sexual exposure (vagina or rectum). There are several ways in which a microbicide might provide this protection. It might contain an active ingredient that blocks HIV activity directly, or it may act as a physical barrier at the mucosal lining of the vagina or rectum.
How will we know if microbicides work?
Every HIV biomedical prevention candidate goes through an extensive series of evaluations, first in laboratory and animal studies and then in humans. The animal studies provide preliminary information about the safety and effectiveness of the candidate. Only those candidates that appear safe in animals are considered for human testing. Efficacy data from animals can also be used to inform decisions about whether to test a candidate in humans. However, studies in animals cannot give a clear answer about whether a strategy will reduce HIV risk in humans. In microbicide animal studies, scientists control exactly when the drug is taken and when the animal is challenged with the infectious virus. Trials in humans provide information about how the strategy works in situations where product usage may not be 100 percent consistent and the timing of potential exposure to HIV is frequently not known.
Microbicide candidates that meet criteria in laboratory and animal studies are moved into small safety studies in humans (Phase I trials). Candidates that appear to be safe and meet certain criteria are then tested in expanded safety studies (Phase II trials). Some of the candidates that complete these stages are moved into large-scale efficacy or effectiveness trials, which may be called Phase III, Phase IIb, test-of-concept, or proof-of-concept trials. There are technical reasons why some trial designs are called efficacy and others are effectiveness studies. Both terms refer to trials that look at whether a candidate reduces the risk of HIV infection. For simplicity, the term efficacy is used below.
The details of these large-scale efficacy studies vary, but the design of microbicide efficacy trials is similar to that of most HIV prevention trials. These trials enroll healthy, HIV-negative people, most commonly in communities where researchers have conducted preparatory work to learn about the rates of risk behaviors and incidence. Each participant receives a basic prevention package including treatment for sexually transmitted infections, condoms, and behavior change counseling. [Unfortunately, needle exchange is not provided in all of the efficacy trials involving injection drug users, and this area is receiving continued attention from advocates and activists.] Some of the participants are randomly assigned to receive the experimental microbicide, while the other participants receive a placebo, a product that is indistinguishable from the experimental microbicide and has no effect on the body. No participant knows whether he or she is receiving the candidate microbicide or placebo. All participants are counseled at every study visit that they can't assume they will be protected by the microbicide and that they cannot know whether they have received the experimental microbicide or the placebo.
Over the course of the trial period, some participants get infected even though they are being counseled and receiving prevention services. This is consistent with what we know about the AIDS epidemic: even with information and services, not everyone can protect himself or herself all the time.
At the end of the trial, researchers compare the rates of new infections in the participants who received the experimental microbicide and in those who received the placebo. If there are significantly fewer new infections in the experimental microbicide group, that is, if the difference is greater than that which can be attributed by chance, this suggests that the microbicide is beneficial.
Where are microbicide trials taking place?
There are nearly 25 clinical trials of experimental microbicides currently underway, in 20 countries, with a concentration in East and Southern Africa. Most of these are small Phase I or Phase II studies. View our world map of ongoing microbicide and other biomedical HIV prevention research trials.
Who is participating in microbicide research?
Like other HIV prevention strategies, microbicide trials are conducted among different populations including gay men and other men who have sex with men, sex workers, and heterosexual men and women in sub-Saharan Africa. Both men and women participate in safety studies for rectal use of microbicides, and men participate in studies to assess penile safety.
When are results expected?
Results from the UK's Microbicide Development Programme's Phase III microbicide efficacy trial, known as MDP 301, are scheduled to be announced in November 2009. MDP 301 is testing the microbicide PRO 2000 to see if it works to reduce the risk of HIV transmission. For more on PRO 2000 and the efficacy trials in which it has been tested, please visit our page on anticipating and understanding the results from trials of the PRO 2000 microbicide candidate.
Results from CAPRISA 004, the first large-scale study of an antiretroviral-containing microbicide, are scheduled to be announced in 2010. In 2013, the VOICE study (MTN 003), another large-scale trial, is scheduled to release results. VOICE is evaluating three different strategies to prevent HIV in women: one ARV-containing microbicide and two different PrEP regimens that consist of taking oral ARVs on a daily basis.
Visit the HIV prevention research timeline and trials map for details on other ongoing biomedical HIV prevention research trials.
Click here for a table of ongoing microbicide trials.